A Traditional Depiction of the Global Water Cycle

Salinity and Evaporation - Precipitation

In contact
with both the oceans and the continents, the thin, transparent atmosphere acts
as a conduit connecting the terrestrial and oceanic components of the water
cycle. Figure 2 is a traditional
depiction of the global water cycle as viewed by hydrologists. It focuses
on the processes of most interest to society, but gives a distorted picture of
the role of the oceans. Relegating the
oceans to a small corner of the diagram conveys a very inaccurate picture. In fact, the oceans cover the majority of the
earth and hold 97% of the free (not chemically bound) water on the planet, comprising both the
primary source of water evaporated into the atmosphere and the main site of
precipitation. We estimate that 86% of global evaporation and 78% of
global precipitation occurs over the oceans. Surely, the oceans deserve a more prominent place in any depiction of
the water cycle!